Reed-blown wind instruments include the clarinet, saxophone, bagpipe, oboe and bassoon. In single reed instruments such as the saxophone and clarinet, a vibrating plate, clamped to the mouthpiece, sets up a standing wave in the barrel of the instrument, and the frequency of these waves is controlled by the musician. The vibrating plate is called the reed, and it is normally made of a natural cane material. The musician creates the vibration by blowing into the gap between the reed and the mouthpiece, which creates and maintains a standing wave in the barrel of the instrument. In the oboe and bassoon, a double reed is used.
Natural cane is the preferred material for the construction of reeds. Apparently, the material properties of natural cane are ideal for the construction of reeds, and reeds made of this material are generally acknowledged to be superior to those made of other materials. Nevertheless, natural cane reeds have many disadvantages. Because the material comes from a natural source, there is a variation in material properties which results in a variation in playing characteristics. Thus, not every reed purchased will be found suitable for playing. Secondly, the reed is hygroscopic, and must be conditioned by exposing it to water or saliva prior to playing. A cane reed that has been properly conditioned with water or saliva is referred to herein as a conditioned cane reed or a reed in its playing condition. Thirdly, cane is prone to splitting along the grain, which causes the reed to become unplayable. Fourthly, the reed material gradually breaks down under the influence of high frequency, low amplitude fatigue to which it is subjected.
As a result of these deficiencies, many inventors have proposed modifications of the reed structure. There have been three basic approaches to produce improved reeds: treatment of natural cane, alternative materials, and alternative materials together with a modified reed configuration.
There is considerable uncertainty in the literature regarding the material properties and configuration required to produce acceptable tonal quality. As a result, in one approach, discussed in U.S. Pat. Nos. 3,340,759, 3,705,820 and 4,145,949, synthetic coatings and penetrating resins are used on the natural cane reed to improve its resistance to water and its durability. Not all of the deficiencies of natural cane are addressed through these methods, however, and so alternative materials and reed configurations have been proposed.
The second principle method of creating an improved reed is to use a material with properties similar to those of cane. However, there is considerable confusion in the literature as to which material and structural properties are important. U.S. Pat. No. 3,420,132 suggests that the stiffness, density and viscous damping are the important material properties, and also discusses several features of the configuration that control the sound quality. U.S. Pat. No. 3,759,132 cites the properties of wet cane, suggesting that these are more important than the properties of dry cane. In U.S. Pat. No. 3,905,268 the ratio of modulus/mass is cited as being important. As used herein, the term modulus is used to denote the elastic modulus or Young's modulus of a material. Furthermore, U.S. Pat. No. 4,355,560 suggests that the individual modulus and density need not be similar to those of cane, provided the ratio of modulus to density (termed the “acoustic impedance”) is similar to that of cane. U.S. Pat. No. 4,014,241 suggests that bending stiffness both transverse and parallel to the long axis of the reed is important. However U.S. Pat. No. 6,087,571 proposes a reed with a conventional shape made from a synthetic material with a matched longitudinal modulus and density, with no attempt to match the transverse modulus or bending stiffness.
The importance of viscous damping is discussed in U.S. Pat. Nos. 3,420,132, 4,337,683, and 5,542,331, but many other patents ignore this property. In U.S. Pat. No. 5,542,331, a means of controlling damping through the inclusion of special damping materials such as hollow fibers is disclosed. U.S. Pat. No. 5,227,572 suggests that the tone of a titanium reed can be controlled by heat treatment to alter the hardness. In this same patent, the failure of previous metal reeds to simulate the “fibratory response of cane” was attributed to the “ductal nature of the metal”.
The preceding discussion indicates that there is still considerable confusion in the art about the important properties of cane for reproducing the tonal qualities of a natural cane reed.
None of the isotropic polymers known in the art with a density sufficiently low to match that of either dry or conditioned cane have an elastic modulus which is as high as that of either dry or conditioned cane in the fiber direction. For example, isotropic polypropylene, with a density of approximately 0.91 g/mL, has an elastic modulus of approximately 1.0 to 2.7 GPa, less than half of the typical modulus of cane in the fiber direction. Polymer-composite materials having sufficient modulus, such as carbon fiber reinforced epoxy, generally have higher densities, as do all metals. In fact, U.S. Pat. No. 3,759,132 teaches that common plastics are unsuitable because of their low modulus and relatively high density, and that composite materials such as glass fiber reinforced plastic are difficult to use because they tend to split.
The density of polymers and composites can be reduced by inclusion of hollow elements, such as hollow glass microballoons. For example, U.S. Pat. No. 4,337,683 proposes the use of graphite/epoxy composite ribs spaced with epoxy/microballoon composite regions to achieve the desired bending stiffness and mass for the reed. U.S. Pat. No. 3,759,132 suggests the use of metal ribs spaced with low density material for the same purpose. However, U.S. Pat. No. 3,420,132 teaches that the last ¼ to ⅜ of an inch of the very tip of the reed controls the elastic response. In this region, the tip may be as thin as 100 micrometers (or 0.004″), and hence complicated ribbed or shaped structures are very difficult to obtain in a reproducible way.
Many investigators consider the linear mass distribution and overall bending stiffness to be more important than the modulus and density of the material used to manufacture the reed, leading to the third principle method of creating an improved reed. These investigators have suggested an overall reed shape which is different to that of the conventional reed in order to deliver the required bending stiffness and mass distribution. Even with materials of low modulus and/or higher density than cane, the bending stiffness to mass ratio can be made equivalent to that of a cane reed by an increase in the cross-sectional moment of inertia.
For example, U.S. Pat. No. 3,905,268 suggests an arched transverse cross-section with longitudinal ridges to produce a higher moment of inertia than that of the conventional cane reed cross-section. In U.S. Pat. No. 4,014,241, a multitude of longitudinal channels are used in a synthetic material, in order to match both the longitudinal and transverse bending stiffness of a cane reed. Cane is anisotropic, with a longitudinal modulus substantially greater than the transverse modulus. Reeds with complex cross-sectional shapes are not generally available commercially, suggesting that this method fails to reproduce the performance of a standard cane reed.
U.S. Pat. No. 6,087,571 discloses a synthetic reed made from an oriented semicrystalline polymer such as polypropylene. Semicrystalline polymers can be uniaxially drawn in the solid state by any one of a number of processes including hydrostatic extrusion, ram extrusion, tensile drawing, die drawing, rolling, or roll-drawing. By uniaxially drawing a semicrystalline polymer at a temperature below its melting temperature, the modulus in the draw direction may be increased to be similar to that of conditioned cane in the fiber direction.
U.S. Pat. No. 6,087,571 discloses a method of manufacturing a synthetic reed comprising the following steps (a) providing a blank of an oriented semi-crystalline polymer having a longitudinal modulus and density which are similar to those of cane; and,
(b) machining the blank to the approximate shape and size of a conventional cane reed while maintaining the temperature in a substantial portion of the oriented polymer blank below the melting temperature of the polymer.
U.S. Pat. No. 6,087,571 states that a uniaxially drawn polymer will preferably have approximately the same modulus as its isotropic precursor in a plane having the draw direction as its normal vector, where the reed is to be machined so that it has a primary vibratory axis parallel to the direction of orientation of the thermoplastic material. U.S. Pat. No. 6,087,571 also discloses another embodiment, in which the oriented semi-crystalline thermoplastic is biaxially oriented to yield elevated modulus and strength in both the transverse and longitudinal directions where the reed is to be machined so that it has a primary vibratory axis parallel to the longitudinal direction.
For a particular instrument, such as the clarinet, a manufacturer will typically produce cane reeds with a variety of cuts and a range of playing strengths. The “cut” of the reed refers to the basic reed shape. Each cut is generally given a particular model name. For single reed instruments, the playing strength is actually a measure of the bending stiffness of the reed parallel to the fiber direction. For a given cut of reed, in order to produce a stiffer reed, most cane reed manufacturers simply machine the reed from cane with a higher elastic modulus, while keeping the thickness and shape similar to those of other reeds of the different strengths.
The longitudinal modulus of oriented polymer reeds can be altered by changing the draw ratio used during solid state deformation. A higher draw ratio leads to more perfect molecular alignment and a higher elastic modulus in the draw direction. Hence it is possible to manufacture a range of strengths for oriented polymer reeds of a particular cut by machining the reeds from material with a range of elastic modulus, mimicking the procedure most commonly used to produce a range of strengths in cane reeds.
U.S. Pat. No. 6,087,571 teaches that an acceptable reed may be machined from an oriented polymeric material with approximately the same modulus as that of the cane in a conditioned cane reed of equivalent playing strength where the modulus is measured parallel to the long axis of the reed, and where the shape and thickness of the oriented polymer reed is also about the same as that of the cane reed of equivalent playing strength.
For uniaxially drawn polymers, U.S. Pat. No. 6,087,571 suggests that transverse modulus of the oriented material is preferably similar to that of its isotropic precursor. For biaxially drawn polymers, U.S. Pat. No. 6,087,571 suggests that transverse modulus of the oriented material is greater than that of its isotropic precursor. In both cases, the transverse bending stiffness of the oriented polymer reed will be higher than that of a cane reed of equivalent playing strength, since the modulus of conditioned cane perpendicular to the fiber direction is significantly lower than that of most isotropic semicrystalline polymers, and in particular, is significantly lower than that of isotropic polypropylene.
U.S. Pat. No. 6,087,571 has been used as the basis for manufacturing commercially successful synthetic reeds by Légère Reeds Ltd. since 1998. Many professional musicians have been satisfied with the quality of the oriented polymer reeds produced according to the teaching of U.S. Pat. No. 6,087,571. Nevertheless, other musicians have expressed the opinion that Légère's synthetic reeds are not as good as the best cane reeds. Specifically, it has been suggested that the synthetic reeds made according to the teachings of U.S. Pat. No. 6,087,571 lack some “warmth” or “color”, where these descriptors are generally used to express some subtlety of the sound, and may be affected by higher order overtones.
Therefore it would be very advantageous to provide synthetic reeds which overcome the aforementioned shortcomings.